Well, you've got two options for that:
1.) Typically, you'd just represent the body as a single capped
cylinder. This doesn't have individual arms getting brushed by boxes
or what have you, but it is far more efficient (and far more suitable
to cases where you've got plenty of characters on-screen at once).
2.) Another option is to represent your character as a ragdoll of
sorts. You take your joint positioning data for each frame of
animation, and set those joint angles as the joint motor target angles
for each ragdoll joint. Then you get your character arms bumping
objects and so on, but you've got a much more expensive method of
collision (and will probably be fairly limited in the number of
enemies you can have like this at once).
-Megan Fox
> Are there any source examples where parts of a character can collide with
> primitives like a ball.
>> I assume it is wise to represent body parts by boxes or cylinders. I'm only
> interested in body parts colliding with objects, not body parts with other
> body parts.